Reconfigurability of a radio frequency (RF) aperture, such as a phased array antenna, is a highly desirable feature so that the radiation characteristics can be changed by modifying the physical and electrical configuration of the array to provide a desired performance metric, such as a desired frequency, scan angle, or impedance.
Prior art phased arrays typically use transmit/receive (TR) modules with phase shifters, amplifiers in each radiation element. A spacing of TR modules that is close to λ/2 or less than λ/2 is generally used to prevent grating lobes, where λ is the wavelength of the center frequency of a transmitted or received signal. A λ/2 or less spacing between the TR modules together with the size or aperture of the phased array antenna determines the number of TR modules required in the phased array antenna. For a given size or aperture of a phased array antenna, it is desirable to have fewer TR modules, because the number of TR modules drives the cost of the phased array antenna.
It is also desirable to be able to reconfigure phased array antenna to achieve different beam patterns. In the prior art this requires reconfiguring the RF feed to the TR modules, and therefore these prior art phased arrays have quite limited reconfigurability.
In the prior art, J. Luther, S. Ebadi, and X. Gong in “A Microstrip Patch Electronically Steerable Parasitic Array Radiator (ESPAR) Antenna with Reactance-Tuned Coupling and Maintained Resonance” IEEE Trans. Antenna Propag., Vol. 60, No. 4, April 2012, pp. 1803-1813 describe using varactors and coupling capacitors between the driven and parasitic patches as means of controlling the coupling for a parasitic phased array. The array elements are fixed and the tuning of the varactors switches the beam. P. W. Hannan, D. S. Lerner, and G. H. Knittel in “Impedance Matching a Phased-array Antenna over Wide Scan Angles by Connecting Circuits”, IEEE Trans. Antenna Propag., Vol. AP-13, January 1965, pp. 28-34 describe the use of connecting circuits between transmission lines to improve the scan impedance and scan performance of a phased array. Phase shifters are used for beam-steering, and an array is described made of wideband elements and using lumped element capacitors/inductors for changing the phase of the signals between the radiating elements.
What is needed is an RF aperture and active phased array antenna that has improved reconfigurability, and that can have a fewer number of TR modules. The embodiments of the present disclosure address these and other needs.